Instituto de Telecomunicações

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Publications

Large-scale LoRa networks: a mode adaptive protocol

Publication . Luís, Miguel; Sargento, Susana; Fernandes, Rui

Low-power wide-area networks (LPWANs) are probably the most promising radio access technologies for Internet-of-Things (IoT) applications. Amongst these, one of the most auspicious solutions is LoRa, a versatile technology highly compatible with urban environments, enabling long-range communications. Most of the LoRa-based medium access protocols operate under the ALOHA rationale, whose performance is known to be fairly poor. This work targets the medium access in single-channel large-scale LoRa networks, proposing a new protocol, denoted as the LoRa mode adaptive protocol (LoRa-MAP), which manages to maintain the best possible connection between end nodes and the gateway, by adapting the LoRa's physical layer parameters and making use of control packets for its coordination without violating the duty-cycle constraints of both end nodes and gateway. An analysis on different medium access schemes is conducted, aiming to perceive how different parameters and network layouts influence the coordination process. An energy expenditure analysis is conducted comparing LoRa-MAP to simpler solutions to study the impact of additional transmission/listening periods. The simulation results have shown that the proposed solution increases the LoRa network scalability, deeming it a great candidate for IoT environments.

2021-09-01Journal article

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3D antenna characterization for WPT applications

Publication . Jordão, Marina; Pires, Diogo; Belo, Daniel; Pinho, Pedro; Carvalho, Nuno Borges

The main goal of this paper is to present a three-dimensional (3D) antenna array to improve the performance of wireless power transmission (WPT) systems, as well as its characterization with over-the-air (OTA) multi-sine techniques. The 3D antenna consists of 15 antenna elements attached to an alternative 3D structure, allowing energy to be transmitted to all azimuth directions at different elevation angles without moving. The OTA multi-sine characterization technique was first utilized to identify issues in antenna arrays. However, in this work, the technique is used to identify which elements of the 3D antenna should operate to transmit the energy in a specific direction. Besides, the 3D antenna design description and its characterization are performed to authenticate its operation. Since 3D antennas are an advantage in WPT applications, the antenna is evaluated in a real WPT scenario to power an RF-DC converter, and experimental results are presented.

2021-06-29Journal article

Open access

Insights from the experimentation of Named Data Networks in mobile wireless environments

Publication . Gameiro, Luís; Senna, Carlos; Luís, Miguel

The Information-Centric Network (ICN) paradigm has been touted as one of the candidates for the Internet of the future, where the Named Data Network (NDN) architecture is the one leading the way. Despite the large amount of works published in the literature targeting new implementations of such architecture, covering different network topologies and use cases, there are few NDN implementations in real networks. Moreover, most of these real-world NDN implementations, especially those addressing wireless and wired communication channels, are at a small scale, in laboratory environments. In this work, we evaluate the performance of an NDN-based implementation in a mobile wireless network, as part of a smart city infrastructure, making use of multiple wireless interfaces. We start by showing how we have implemented the NDN stack in current network nodes of the smart city infrastructure, following a hybrid solution where both TCP/IP and NDN paradigms can coexist. The implementation is evaluated in three scenarios, targeting different situations: mobility, the simultaneous use of different wireless interfaces and the network characteristics. The results show that our implementation works properly and insights about the correct NDN parameterization are derived.

2022-06-27Journal article

Open access

Improving LoRa network simulator for a More realistic approach on LoRaWAN

Publication . Francisco, Sérgio; Pinho, Pedro; Luís, Miguel

Nowadays, the need for information is rapidly increasing, urging the development of technology to obtain reliable information. Under the scope of Smart Cities, Low Power Wide Area Networks (LPWANs) have been seen as one of the enabling technologies for the data gathering process but, the evaluation of new methods and solutions in large-scale, real world-scenarios, is a challenging and sometimes an impossible task. Thus, the need to use tools enabling the simulation of such networks arose, triggering the development of different network simulators. In this work we focus on the simulation of LoRa networks. Resorting on the LoRa network simulator mostly used in the literature, the LoRaSim, we study the impact of different propagation and the capture-effect models in the performance of a LoRa network. In addition, an extension to LoraSim is implemented, offering the capability to tweak the network on a more detailed fashion, by supporting distinguished parameters (spreading factor, bandwidth, code rate and payload) on the end-devices. Results show that when applying a well-known propagation model (Okumura-Hata) and a more realistic capture-effect on a network that emphasizes the use of orthogonality among all devices, this heterogeneity greatly increases its efficiency and quality.

2021-05Conference object

Restricted access

MobiWise: eco-routing decision support leveraging the internet of things

Publication . Aguiar, Ana; Fernandes, Paulo; Guerreiro, Andreia P.; Tomás, Ricardo; Agnelo, João; Santos, José Luís; Araújo, Filipe; Coelho, Margarida C.; Fonseca, Carlos M.; D'Orey, Pedro; Luís, Miguel; Sargento, Susana

Eco-routing distributes traffic in cities to improve mobility sustainability. The implementation of eco-routing in real-life requires a diverse set of information, including different kinds of sensors. These sensors are often already integrated in city infrastructure, some are technologically outdated, and are often operated by multiple entities. In this work, we provide a use case-oriented system design for an eco-routing service leveraging Internet-of-Things (IoT) technologies. The methodology involves six phases: (1) defining an eco-routing use case for a vehicle fleet; (2) formulating a routing problem as a multi-objective optimisation to divert traffic at a relevant hub facility; (3) identifying data sources and processing required information; (4) proposing a microservice-based architecture leveraging IoT technologies adequate to a multi-stakeholder scenario; (5) applying a microscopic traffic simulator as a digital twin to deal with data sparsity; and (6) visually illustrating eco-routing trade-offs to support decision making. We built a proof-of-concept for a mid-sized European city. Using real data and a calibrated digital twin, we would achieve hourly total emissions reductions up to 2.1%, when applied in a car fleet composed of 5% of eco-routing vehicles. This traffic diversion would allow annual carbon dioxide and nitrogen oxides savings of 400 tons and 1.2 tons, respectively.

2022-10Journal article

Open access